The present invention relates to an air-bag, and more particularly relates to an air-bag having a vent hole formed therein.
It is known to be desirable to vent an air-bag provided for use as a safety arrangement in a motor vehicle to protect an occupant of the vehicle in the event that an accident should occur. It is known to be particularly important to vent an air-bag if the air-bag is of the type intended to provide protection in the event that a front impact should occur.
An air-bag that is intended to provide protection in the case that a front impact should occur is generally located so that, when inflated, the air-bag is positioned in front of the occupant of the vehicle to be protected. During the front impact, the motor vehicle will decelerate very suddenly. Due to inertia, the occupant of the vehicle tends to continue moving, and thus the occupant of the vehicle is, in effect, moving forwardly relative to the rest of the vehicle, and thus the occupant moves forwardly relative to the air-bag itself. The function of the air-bag is to decelerate the occupant, preferably in such a way that the occupant suffers no or only relatively slight injuries. The air-bag must be inflated very swiftly in the event of an accident and thus, typically, contains relatively high-pressure gas when inflated. If the air-bag were not vented, then because of the high pressure of gas within it, the air-bag would not decelerate the occupant gently, but instead would stop the occupant extremely swiftly and hence may injure the occupant. It is thus known to provide air-bags with one or more vent holes formed in them so that, when the air-bag is struck by the occupant in a crash situation, gas can escape from the air-bag through the vent hole or holes, so that the air-bag serves the function of decelerating the occupant more gently, to avoid serious injury.
It has been found to be advantageous to configure the or each vent hole of an air-bag so that the venting flow of gas passing through the vent hole as an occupant strikes the air-bag can be directed along a predefined flow path. It is particularly advantageous to be able to direct the flow of venting gas from the interior of the air-bag, away from the occupant, because typically, the gas used to inflate air-bags in motor vehicles is generated at high temperature which can cause serious burns if it is directed towards an occupant during a crash situation.
JP01277991-A discloses a prior arrangement to direct the venting flow of gas from the interior of an air-bag, such that the gas flows in directions substantially tangential to the outermost surface of the air-bag rather than generally orthogonal to the outermost surface of the air-bag. This is achieved by providing each vent hole with a cover flap which is configured to form a duct to direct the venting gas flow as desired. However, the provision of a separate fabric cover over the vent hole, in addition to the fabric of the air-bag, is considered to be disadvantageous, because it necessitates stitching together of the two pieces of fabric, thereby complicating the manufacturing process to produce the air-bag.
It is therefore an object of the present invention to provide an improved air-bag having a vent hole formed therein.
Accordingly, the present invention provides an air-bag having a vent hole formed therein, the periphery of the vent hole having first and second opposed parts, wherein a tuck is formed in the air-bag in the region of said first part such that said second part extends past said first part in a direction extending substantially outwards from the interior volume of the air-bag, when the air-bag is inflated.
Numerous embodiments and implementations of the invention may be implemented, including:                a) The tuck defines a pleat in the air-bag;        b) The tuck is tapered;        c) The tuck is formed by a fold in the air-bag, the fold intersecting the first part of the vent hole periphery;        d) The tuck is at least partly defined by a seam intersecting said first part of the vent hole;        e) The tuck is formed by stitching together two regions of the air-bag;        f) The tuck is formed so as to lie inside the interior volume of the air-bag;        g) The tuck is folded and secured against the interior surface of the air-bag; and        h) The tuck is secured against the interior of the air-bag by stitching.        
Conveniently, the air-bag has a plurality of said vent holes, each vent hole having a respective said tuck provided in the region of its periphery.
So that the invention may be more readily understood, and so that further features thereof may be appreciated, embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: